Ice ages can cause the extinction of animals because lack of

Warmth and vegetation were the two big things. Since everything was ice, animals would've died of hypothermia or something, and the ice wouldn't allow any vegetation to grow. It's kind of like the dinosaurs; the plant eaters died b/c they didn't have any vegetation to eat, and the meat eaters died b/c they didn't have any meat to eat since the animals died. Same thing happened in the ice ages. Just with the added variable of freezing temperatures.